"nervous," 1869, from jump (n.) in a sense "sudden involuntary movement" + -y (2). Related: Jumpiness. The jumps "state of nervous excitement" is from 1872.
Entries linking to jumpy
jump n.
1550s, "an act of jumping," from jump (v.). Figurative meaning "sudden abrupt rise" is from 1650s. Meaning "abrupt transition from one point to another" is from 1670s. Sense of "a parachute descent" is from 1922. Meaning "jazz music with a strong beat" first recorded 1937, in Count Basie's "One O'Clock Jump." Jump suit "one-piece coverall modeled on those worn by paratroopers and skydivers" is from 1948. To get a jump on "get ahead, get moving" is from 1910, perhaps a figurative use from the jump-spark that ignites an engine.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.